Fuel cell unit

Abstract

The invention relates to a fuel cell unit (1) for electrochemically generating electrical energy, comprising: fuel cells (4) arranged in a stack and forming a fuel cell stack (3); a humidifier (37) for transferring moisture and / or water of the oxidant off-gas drawn from the fuel cell stack (3) into the oxidant introduced into the fuel cell stack (3); at least one fastener (45) on which the humidifier (37) is fastened; at least one fastening device (49) by means of which the humidifier (37) is fastened to the fastening device (45), the fuel cell unit (1) comprising at least one sliding bearing (50) having a first sliding bearing part (51) and a second sliding bearing part (52), such that the humidifier (37) is fastened to the fastening device (45) by means of the fastening device (49) by means of the fastening device (49) by means of the first and second sliding bearing parts (51, 52). 52) enables a relative movement between the humidifier (37) and the at least one fastener (45) to compensate for thermal expansion and / or thermal compression.

Description

Technical Field

[0001] The invention relates to a fuel cell unit according to the preamble of claim 1 and to a fuel cell system according to the preamble of claim 15 . Background Art

[0002] Fuel cell units are direct current cells that convert continuously supplied fuel and oxidant into electrical energy and water by means of redox reactions at the anode and cathode. Fuel cells are used in a wide variety of stationary and mobile applications, for example in buildings not connected to the power grid or in motor vehicles, in rail transport, in aviation, in space travel and in navigation. In a fuel cell unit, a large number of fuel cells are arranged to form a fuel cell stack.

[0003] There is a gas space for the oxidant inside the fuel cell, that is to say, a flow space for the passage of the oxidant (for example, air with oxygen from the environment). The gas space for the oxidant is composed of channels on the bipolar plates and of a gas diffusion layer for the cathode. Therefore, the channel is composed of the corresponding channel structure of the bipolar plate, and the oxidant (ie, oxygen) reaches the cathode of the fuel cell via the gas diffusion layer. Similarly, a gas space for the fuel is constructed on the anode.

[0004] A fuel cell system is constructed from various components, such as a fuel supply system, an oxidant supply system, and a fuel cell stack. A proton exchange membrane is present in the fuel cell for conducting protons.

[0005] In order to make the proton exchange membrane fully conductive, it is necessary to fully humidify the proton exchange membrane. For example, the moisture of the oxidant exhaust gas drawn from the fuel cell stack is transferred to the oxidant to be supplied to the fuel cell stack by means of a humidifier. The humidifier is fastened to the fasteners of the main bracket of the fuel cell system by means of a fastening device. The housing of the humidifier is constructed of plastic, while the main bracket with the fasteners is constructed of metal. Plastic and metal have different thermal expansion coefficients. Therefore, in the presence of temperature fluctuations, large tensile and compressive forces will be generated on the fastening device, which may trigger the fastening device or the housing of the humidifier to fail or be damaged in an unfavorable manner.

[0006] DE 10 2020 211 882 A1 discloses a humidifier with a housing for a fuel cell system, the humidifier having: a substantially cylindrical hood-shaped middle piece for receiving a membrane and two end caps for fluid-tightly closing the middle piece, wherein an inlet connection for introducing wet exhaust gas from the fuel cell system into the humidifier and an outlet connection for conducting dehumidified exhaust gas from the fuel cell system out of the humidifier are provided on the middle piece.

[0007] DE 10 2012 018 863 A1 shows a gas / gas humidifier having a dry side, through which dry gas to be humidified flows, and a wet side, through which moist gas as a moisture provider flows, having a membrane permeable to water vapor, which separates the moist side from the dry side, wherein a liquid separator is integrated behind the membrane in the flow direction of the moist gas. Summary of the invention

[0008] The fuel cell unit according to the present invention is used to generate electrical energy electrochemically, and comprises: fuel cells arranged in a stack and the stacked fuel cells forming a fuel cell stack; a humidifier for transferring moisture and / or water from the oxidant exhaust gas drawn out of the fuel cell stack to the oxidant introduced into the fuel cell stack; at least one fastener, on which the humidifier is fastened; and at least one fastening device, by means of which the humidifier is fastened to the fastener, wherein the fuel cell unit comprises at least one sliding bearing having a first sliding bearing component and a second sliding bearing component, so that relative movement can be implemented between the humidifier and the at least one fastener by means of a sliding movement between the first and second sliding bearing components to compensate for thermal expansion and / or thermal compression.

[0009] In a further embodiment, at least one plain bearing is integrated in a respective one of the fastening devices.

[0010] In an additional variant, the length of the relative movement that can be performed between the respective first and the respective second plain bearing part is between 0 mm and 10 mm, in particular between 1 mm and 5 mm.

[0011] In a supplementary embodiment, at least one first plain bearing part is designed as a plain bearing bushing and / or as a boundary of a bore hole and / or at least one second plain bearing part is designed as a bolt.

[0012] In another embodiment, the bolt is fastened indirectly or directly to the humidifier and the plain bearing bushing is fastened indirectly or directly to the fastening element, or vice versa.

[0013] Preferably, the first and the second plain bearing part are arranged one above the other in the contact region.

[0014] In an additional variant, the fuel cell unit comprises at least one encapsulation for sealing and / or shielding the contact area between the first and second plain bearing parts with respect to the environment.

[0015] In particular, at least one space in the region of a respective one end of the contact region between the respective first and the respective second plain bearing part is filled, in particular completely filled, by means of a respective encapsulation, and preferably the space is formed outside the contact region. Preferably, at least one space in the region of a respective one end of the contact region has a spacing of less than 12 mm or 6 mm to a respective one associated end, in particular an axial end, of the contact region.

[0016] In a further embodiment, a respective plain bearing has two ends at the contact region between the first and second plain bearing parts, and both ends are sealed and / or shielded by means of a respective encapsulation.

[0017] In a further embodiment, the encapsulation is placed on the first and second plain bearing parts of a respective plain bearing, in particular on the axial ends of the first and second plain bearing parts, in particular in the region of the ends of the contact region between the first and second plain bearing parts, preferably in the region of the axial ends.

[0018] In a supplementary configuration, the geometry of a respective contact area sealed by the encapsulation corresponds substantially, in particular in cross section, to the geometry of the encapsulation. For example, the contact area and the encapsulation are designed annularly or squarely in cross section. Preferably, the cross section is oriented perpendicularly to the longitudinal axis of the plain bearing and / or the fastening device.

[0019] Practically, the contact region and the encapsulation are designed to be annular and / or circular in cross section.

[0020] In a further embodiment, the encapsulation placed on the respective one end of the contact region extends beyond the contact region in a radial direction, in particular in both radial directions, preferably by at least 1 mm or 3 mm and / or by less than 30 mm or 10 mm.

[0021] Preferably, at least one encapsulation is made of elastic plastic, preferably neoprene or rubber.

[0022] The fuel cell system according to the present invention is used to convert chemical energy into electrical energy, and comprises: at least one fuel cell unit; at least one oxidant supply system for an oxidant; at least one fuel supply system; at least one cooling system, wherein the fuel cell unit is constructed as the fuel cell unit described in the present patent application.

[0023] In another variant, the at least one encapsulation is configured as a seal.

[0024] Preferably, at least one encapsulation is designed as a cover, in particular a pot-shaped cover, and, in particular, the encapsulation as a cover has a distance to an associated axial end of the contact region.

[0025] In a supplementary embodiment, at least one first plain bearing part is designed as a boundary of a recess and / or at least one second plain bearing part is designed as a projection.

[0026] In an additional variant, at least one of the first and / or the second plain bearing part is designed to be circular, oval or rectangular, in particular square, in cross section.

[0027] In particular, at least one annular space in the region of a respective one end of the contact region between the respective first and the respective second plain bearing part is filled, in particular completely filled, by means of a respective encapsulation, and preferably the annular space is formed outside the contact region. Preferably, at least one annular space in the region of a respective one end of the contact region has a spacing of less than 12 mm or 6 mm to a respective one associated end, in particular an axial end, of the contact region.

[0028] In a supplementary variant, the encapsulation, in particular the seal, is at least partially, in particular completely, constructed from an elastic material and / or from an elastomer and / or from a plastic, preferably from HPU and / or PU and / or NBR and / or FPM and / or FKM and / or EPDM and / or silicone and / or PTFE and / or POM and / or PA and / or PA6G and / or rubber.

[0029] In an additional embodiment, the material of the encapsulation has an elastic modulus between 0.05 and 10 GPa, in particular between 0.1 and 5 GPa.

[0030] In a further embodiment, the fuel cell unit, in particular the fuel cell stack, comprises an opening for introducing an oxidant into the fuel cell stack.

[0031] In a further embodiment, the fuel cell unit, in particular the fuel cell stack, comprises an opening for conducting the oxidant conducted through the fuel cell stack out of the fuel cell stack as oxidant waste gas.

[0032] In a further embodiment, the fastening element is made of metal, in particular steel and / or aluminum.

[0033] Practically, the dehumidifier comprises at least one membrane for transferring moisture and / or water.

[0034] In an additional variant, the humidifier, in particular the housing of the humidifier, is formed from plastic.

[0035] In another embodiment, the fastening element is a component of an overall support for the fuel cell system and / or the fastening element is fastened to the overall support for the fuel cell system.

[0036] In another embodiment, the overall support comprises at least one plate and / or at least one grid and / or at least one truss.

[0037] The overall carrier is preferably constructed in one piece or in multiple pieces.

[0038] In a supplementary variant, the overall support is at least partially, in particular completely, made of metal, in particular steel, in particular stainless steel and / or aluminum.

[0039] In a supplementary variant, the plain bearing bushing is formed from a non-ferrous metal, for example copper, nickel and / or zinc.

[0040] In another embodiment, the extension and / or length of the contact area in the circumferential direction at the axial end of the contact area is substantially equivalent to the extension and / or length of the shield in the circumferential direction at the radial end of the shield, in particular with a deviation of less than 30%, 20% or 10%.

[0041] In a supplementary embodiment, a polymer coating, for example made of polytetrafluoroethylene (PTFE), is formed on the radial inner side and / or radial outer side of at least one plain bearing component. The polymer coating reduces the friction between the plain bearing components.

[0042] In a further variant, the contact region of the first and second plain bearing parts is designed to be flat and / or smooth and / or cylindrical hood-like.

[0043] In a supplementary embodiment, at least one gas conveying device is designed as a blower and / or a compressor and / or a compressor.

[0044] In another embodiment, the fuel cell each comprises an ion exchange membrane (in particular a proton exchange membrane and / or an anion exchange membrane), an anode, a cathode, at least one gas diffusion layer and a bipolar plate.

[0045] Preferably, the fuel is hydrogen, a hydrogen-rich gas, reformed gas or natural gas.

[0046] Practically, the fuel cell and / or components of the fuel cell are of substantially flat and / or disk-shaped design.

[0047] In another variant, the fuel cell unit comprises a housing and / or a connection plate. The fuel cell group or fuel cell stack is surrounded by the housing and / or the connection plate. Preferably, the fuel cell unit comprises a fuel cell stack and preferably a housing.

[0048] In a supplementary variant, the oxidant is air with oxygen or pure oxygen.

[0049] Preferably, the fuel cell unit is a PEM fuel cell unit with a PEM fuel cell or a SOFC fuel cell unit with a SOFC fuel cell or an alkaline fuel cell (AFC). BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Hereinafter, embodiments of the present invention will be described in more detail with reference to the accompanying drawings. It shows:

[0051] Figure 1 Simplified diagram of a fuel cell system,

[0052] Figure 2 A first view of a humidifier for a fuel cell system without showing the encapsulation of the sliding bearing,

[0053] Figure 3 A second view of a humidifier for a fuel cell system showing the encapsulation of the sliding bearing,

[0054] Figure 4 Without showing the encapsulation of the sliding bearing Figure 2 Detailed view of a fastening device with a sliding bearing,

[0055] Figure 5 In the case of the encapsulation of the sliding bearing shown in Figure 3 Detailed view of a fastening device with a sliding bearing, and

[0056] Figure 6 according to Figure 5 A longitudinal section through a fastening device having a sliding bearing. DETAILED DESCRIPTION

[0057] exist Figure 1 1 , the fuel cell unit 1 is shown as a fuel cell group 3, that is, as a fuel cell stack. The fuel cell unit 1 comprises a fuel cell stack 3, a housing 13 and a connecting plate 15. The housing 13 delimits an interior space 14. The connecting plate 15 also functions as a housing 13 and is fixed to the rest of the housing 13 by means of fixing elements 16, in particular screws 17. In the fuel cell stack 3, the fuel cells 4 are stacked and arranged in an aligned manner as PEM fuel cells 5. Due to the large number of stacked fuel cells 4, from about 300 to 400 fuel cells 4, they are not shown in FIG. 1 for reasons of simplicity. Figure 1 The principle of the fuel cell 4 is to generate electrical energy or current by means of an electrochemical reaction. 2The gaseous fuel is guided to the anode (not shown) as a recirculating fuel, and the anode constitutes the negative electrode. The gaseous oxidant (i.e., air with oxygen) is guided to the cathode (not shown), that is, the oxygen in the air provides the required gaseous oxidant. Reduction (electron reception) occurs on the cathode. Oxidation (as electron release) is implemented on the anode. In addition, the fuel cell 4 includes an ion exchange membrane as a proton exchange membrane (Proton Exchange Membrane, PEM), which is arranged between the anode and the cathode. The electrodes are placed on both sides of the PEM facing the gas space as an anode and a cathode (not shown). The unit composed of the PEM, the anode and the cathode is called a membrane electrode assembly (Membran Electrode Assembly, MEA) (not shown). The gas diffusion layer (Gas Diffusion Layer, GDL) is placed on the anode and the cathode. The bipolar plate (not shown) is placed on the GDL. The conductive bipolar plate is used as a collector for drainage and for guiding the reaction gas.

[0058] In the fuel cell unit 1, the fuel cell 4 is arranged between two clamping elements 18 as clamping plates 19. The upper clamping plate 20 is placed on the uppermost fuel cell 4, and the lower clamping plate 21 is placed on the lowermost fuel cell 4. The clamping element 18 applies a pressure to the fuel cell 4, that is, the upper clamping plate 20 is placed on the uppermost fuel cell 4 by pressure, and the lower clamping plate 21 is placed on the lowermost fuel cell 4 by pressure. The fuel cell stack 3 is thereby tightened to ensure the sealing of the fuel, oxidant and coolant, especially based on elastic sealing, and in addition to keep the electrical contact resistance inside the fuel cell stack 3 as small as possible. In order to tighten the fuel cell 4 with the clamping element 18, four connecting devices 22 are constructed on the fuel cell unit 1 as bolts 23, which are loaded with tensile force. The four bolts 23 are firmly connected to the clamping plate 19.

[0059] Openings are formed in the connecting plate 15 and in the lower clamping plate 21 for introducing recirculating fuel into the channel for recirculating fuel. In addition, openings are formed in the connecting plate 15 and in the lower clamping plate 21 for leading the recirculating fuel out of the recirculating fuel channel. Openings 35 for introducing oxidant and openings 36 for leading oxidant out, as well as openings (not shown) for introducing coolant and leading coolant out, are formed in the connecting plate 15 and in the lower clamping plate 21 as the clamping element 18. Thus, a total of 6 openings (in Figure 1 (only partially shown in FIG.

[0060] In addition to the fuel cell unit 1, the fuel cell system 2 includes an oxidant supply system 26 for supplying air as an oxidant to the fuel cell stack 2. The oxidant supply system 26 includes a gas delivery device 27 (e.g., a blower), a compressor, a turbo compressor driven by an electric motor and / or a turbine (not shown), an oxidant pipe 28 as an oxidant supply pipe 24 and an oxidant outlet pipe 25, and a humidifier 37.

[0061] In addition to the fuel cell unit 1, the fuel cell system 2 also includes a fuel supply system 29 for supplying the fuel cell stack 3 with hydrogen as fuel. The fuel supply system 29 includes a pressure vessel 30, a fuel pipe 31 as a process fluid pipe, a valve for fuel (not shown), in particular an injector (not shown) for controlling the fuel volume flow introduced from the fuel pipe 31 into the recirculation pipe 32, a heat exchanger (not shown) for the fuel, a pressure reducer (not shown), a recirculation fuel pipe 32 as a process fluid pipe, a recirculation fuel delivery device 33, an electric motor (not shown) for driving the recirculation fuel delivery device 33 and a water separator 34 for separating water from the recirculation fuel, a water container (not shown) for collecting water accumulated in the water separator 34, a discharge valve (not shown) for discharging water from the water container and a discharge valve (not shown) as a purge valve for discharging the recirculation fuel into the environment. In the fuel supply system 29 for supplying the fuel cell stack 3 with hydrogen as fuel, hydrogen stored in the pressure vessel 30 at a high pressure of, for example, 400 bar is supplied to the fuel cell 4 through the fuel pipe 31. After the fuel is guided through the fuel cell 4, the hydrogen is not completely consumed, so that the hydrogen drawn from the fuel cell 4 is supplied to the fuel cell 4 again through the recirculation fuel pipe 32 in the loop. A recirculation fuel delivery device 33 is used to deliver the recirculation fuel through the recirculation fuel pipe 32. After the fuel is guided through the fuel cell 4, the moisture content of the fuel increases, so that in order to avoid high water content or moisture content in the recirculation fuel, the fuel supply system 29 has a water separator 34. The water deposited in the water separator 34 accumulates in a water container not shown and is discharged into the environment through a discharge valve (not shown). Excess recirculation fuel is discharged into the environment via a purge valve not shown.

[0062] In addition to the fuel cell unit 1, the fuel cell system 2 also includes a cooling system (not shown) for regulating the temperature of the fuel cell stack 3 (i.e., for cooling the fuel cell stack 3). The cooling system for regulating the temperature of the fuel cell stack 3 includes a coolant pipe as a process fluid pipe, a heat exchanger, and a pump for turning the coolant. The coolant is introduced into the bipolar plate of the fuel cell 4 via the coolant channel, and heat is released to the environment on the heat exchanger. In addition to the fuel cell unit 1, the fuel cell system 2 also includes an oxidant supply system 26, a fuel supply system 29, and a cooling system not shown as a coolant supply system.

[0063] The proton exchange membrane of the fuel cell 4 must be sufficiently moistened to conduct protons. For this reason, the fuel cell system 2 has a humidifier 37. The humidifier 37 transfers or guides the moisture and / or water of the oxidant exhaust gas drawn from the fuel cell stack 3 in the oxidant outlet pipelines 25, 28 to the oxidant in the oxidant supply pipes 24, 28. For this purpose, a corresponding membrane (not shown) is constructed in the humidifier 37 to transfer or guide the moisture and / or water of the oxidant exhaust gas to the oxidant introduced into the fuel cell stack 3.

[0064] The humidifier 37 comprises a multi-piece housing 38 made of plastic. An opening 41 for introducing the oxidant to be introduced into the fuel cell stack 3 and an opening 42 for leading out the oxidant to be introduced into the fuel cell stack 3 are constructed in the housing 38. In addition, an opening 43 for introducing the oxidant exhaust gas led out of the fuel cell stack 3 and an opening 44 for leading out the oxidant exhaust gas led out of the fuel cell stack 3 are constructed on the housing 38 of the humidifier 37. The openings 41, 42, 43 and 44 are constructed on the corresponding pipes. Two circumferential flanges 39 are constructed on the housing 38. The housing 38 and therefore also the two flanges 39 are constructed of plastic. A fixing ring 40 made of metal is fastened to the corresponding flange 39 by means of screws 46. The screws 46 have a screw head 47 and a screw shaft 48 with an external thread. A bore 73 ( Figure 6 ) and the external thread of the screw shaft 48 of a corresponding screw 46 is screwed into these bore holes 73 with internal threads.

[0065] The fuel cell system 2 comprises a main support (not shown) on which the fuel cell stack 3, the oxidant supply system 26, the fuel supply system 29 and the coolant system are fastened. The main support (not shown) is designed, for example, as a plate or a truss. As a component of the main support, the fastener 45 is fastened to the main support as a substantially rod-shaped support. The humidifier 37 is fastened by means of two fasteners 45 and is Figure 2 and Figure 3 Only one fastener 45 is shown. The humidifier 37 is fastened to the Figure 2 and Figure 3 In addition, a sliding bearing 50 is integrated in the fastening device 49, wherein the sliding bearing 50 also acts as a fastening device 49. Two bores are formed in the fastening device 45 and a sliding bearing bushing 53 ( Figure 6). The plain bearing bushing 53 has a radial inner side 54, and the bolt 55 is arranged in the borehole in a manner limited by the radial inner side 54 of the plain bearing bushing 53. The bolt 55, which is approximately cylindrical and hood-shaped as a hollow bolt 55, has a radial outer side 56, and the radial outer side 56 of the bolt 55 is placed on the radial inner side 54 of the plain bearing bushing 53 at the contact area 57. The plain bearing bushing 53 and the bolt 55 are coaxial with the longitudinal axis 70 and are oriented concentrically to each other. The longitudinal axis 70 is the longitudinal axis 70 of the plain bearing 50 and the fastening device 49. The diameter of the radial outer side 56 of the bolt 55 at the contact area 57 is the same as or slightly smaller than the diameter of the radial inner side 54 of the plain bearing bushing 53. The axial direction 71 is oriented in the direction of the longitudinal axis 70, while the radial direction 72 is oriented perpendicularly to the axial direction 71 or perpendicularly to the central longitudinal axis 70. The contact area 57 has two axial ends 58, 59, namely a first axial end 58 and a second axial end 59. The first axial end 58 of the contact region 57 faces away from the fixing ring 40 and the fastening element 45, just like the first axial end 60 of the bolt 55. The second axial end 59 of the contact region 57 faces the fixing ring 40 and the fastening element 45. The second axial end 61 of the bolt 55 is configured opposite the first axial end 60 of the bolt 55. In the region of the first axial end 60 of the bolt 55 or in the vicinity thereof, the first stop 62 is configured as a completely surrounding first stop ring 63. Between the first axial end 60 and the second axial end 61, the second stop 64 is configured as a completely surrounding second stop ring 65. The second stop 64 is arranged between the fixing ring 40 and the fastening element 45 in the axial direction 71 ( Figure 6 ).

[0066] The bolt 45 has a central bore 66. An internal thread 67 is formed on the end region of the bolt 45 in the region of the second axial end 61. The bolt 45 is arranged in the bore 73 on the fixing ring 40 in the region of the second axial end 61. The screw 46 with the external thread on the screw shank 48 is screwed into the internal thread 67 on the bore 66 of the bolt 55, so that the fixing ring 40 is clamped in the region of the bore 73 between the screw head 47 of the screw 46 on the one hand and the second stop 64 as the second stop ring 65 on the other hand and is thus fixed in a non-positive manner. In addition, due to the geometry of the bore 73, the screw 46 and the second stop 64, the bolt 55 is also fixed in a positive manner on the fixing ring 40.

[0067] The length and / or extension of the sliding bearing bushing 53, in particular the radial inner side 54 of the sliding bearing bushing 53, in the axial direction 71 is approximately 5 mm greater than the spacing between the first stop 62 and the second stop 64 in the axial direction 71. Therefore, in the axial direction 71, the sliding movement can be implemented as a relative movement of slightly less than 5 mm between the sliding bearing bushing 53 as the first sliding bearing component 51 and the bolt 54 as the second sliding bearing component 52. Therefore, the first sliding bearing component 51 and the second sliding bearing component 52 form the sliding bearing 50. The first stop 62 as the first stop ring 63 has a radial spacing to the longitudinal axis 70 that is greater than the radial spacing from the longitudinal axis 70 to the radial inner side 54 of the sliding bearing bushing 53. Therefore, the first stop ring 63 prevents the bolt 55 from moving out of the borehole delimited by the sliding bearing bushing 53 and thus fastens the bolt 55 to the fastening element 45 in a form-fitting manner.

[0068] The annular encapsulation 68 is arranged as an annular seal 69 at the annular space in the region of the first axial end 58 of the contact region 57. Thus, the encapsulation 68 is arranged in the axial direction 71 between the first end 58 of the contact region 57 and the first stop 62. In a similar manner, another annular encapsulation 68 is arranged as an annular seal 69 at the annular space in the region of the second axial end 59 of the contact region 57. The contact regions 57 on the radial inner side 54 of the plain bearing bushing 53 and on the radial outer side 56 of the bolt 55 may be damaged due to contamination and corrosion, so that they are no longer smoothly constructed and thus prevent sliding movement between the first plain bearing component 51 and the second plain bearing component 52. When arranged in a motor vehicle, the plain bearing 50 is subject to environmental influences, such as environmental influences caused by pollution particles in the air or in rainwater. In addition, corrosion, such as corrosion caused by deicing salt, may also occur on the plain bearing 50. The encapsulation 68 substantially prevents the penetration of matter into the plain bearing 50, that is, into the intermediate space or contact region 57 between the radial inner side 54 of the plain bearing bushing 53 and the radial outer side 56 of the bolt 55. The encapsulation 68 is designed as an elastic seal 69 made of rubber or foam material. As a result, the sliding movement between the first and second plain bearing parts 51, 52 can also be carried out by reducing the axial expansion of the seal 69, in that the expansion of the seal 69 in the axial direction 71 is reduced due to the elastic properties of the seal 69 due to the pressure acting on the seal 69 in the axial direction 71. In addition, the seal 69 also acts as a damping element to prevent undesired vibrations and / or collisions between the first plain bearing part 51 and the second plain bearing part 52. In contrast, the encapsulation 68 may also be constructed of metal, for example as a pot-shaped or annular cover in the region of the axial ends 58, 59 of the contact region 57, preferably at a distance to the axial ends 58, 59 in the associated contact region 57. The encapsulation 68 does not necessarily have to achieve a complete sealing of the contact region 57, but may also simply act as a protection against splash water.

[0069] Overall, the fuel cell unit 1 according to the invention and the fuel cell system 2 according to the invention have important advantages. In addition, the sliding bearing 50 is integrated into the fastening device 49. The plastic of the housing 38 of the humidifier 37 has a significantly different thermal expansion coefficient than the fastening element 45 and the overall bracket made of metal. As a result, high tensile forces or compressive forces may occur on the fastening device 49 due to different thermal expansion or thermal compression caused by temperature. The sliding bearing 50 prevents the high tensile forces or compressive forces generated thereby on the fastening device 49, so that failure of the fastening device 49 due to high tensile forces or compressive forces can be basically ruled out. In addition, the sliding bearing 50 is provided with an encapsulation 68. The encapsulation 68 prevents contamination particles or corrosion-inducing substances from entering the contact area 57 of the sliding bearing 50. Therefore, the jamming of the sliding bearing 50, which is triggered by, for example, contamination particles or corrosion-inducing substances, can be basically avoided.

Claims

1. A fuel cell unit (1) for electrochemically generating electrical energy, comprising: - fuel cells (4) arranged in a stack, and the stacked fuel cells (4) constitute a fuel cell stack (3); - a humidifier (37) for transferring moisture and / or water from the oxidant off-gas drawn out from the fuel cell stack (3) to the oxidant introduced into the fuel cell stack (3); - at least one fastener (45) to which the humidifier (37) is fastened; at least one fastening device (49), by means of which the humidifier (37) is fastened to the fastening element (45), It is characterized in that The fuel cell unit (1) comprises at least one sliding bearing (50) having a first sliding bearing component (51) and a second sliding bearing component (52), so that a relative movement between the humidifier (37) and the at least one fastener (45) can be implemented by means of a sliding movement between the first and second sliding bearing components (51, 52) to compensate for thermal expansion and / or thermal compression.

2. The fuel cell unit according to claim 1, It is characterized in that The at least one sliding bearing (50) is integrated into the corresponding fastening device (49).

3. The fuel cell unit according to claim 1 or 2, It is characterized in that The length of the relative movement that can be performed between the respective first plain bearing part (51) and the respective second plain bearing part (52) is between 0 mm and 10 mm, in particular between 1 mm and 5 mm.

4. A fuel cell unit according to any one or more of the preceding claims, It is characterized in that The at least one first plain bearing component (51) is designed as a plain bearing bushing (53) and / or as a boundary of a bore hole, and the at least one second plain bearing component (52) is designed as a bolt (55).

5. The fuel cell unit according to claim 4, It is characterized in that The bolt (55) is fastened directly or indirectly to the humidifier (37), and the plain bearing bushing (53) is fastened directly or indirectly to the fastening element (45), or vice versa.

6. A fuel cell unit according to any one or more of the preceding claims; It is characterized in that The first and second sliding bearing parts (51, 52) are arranged one above the other in a contact area (57).

7. A fuel cell unit according to any one or more of the preceding claims, It is characterized in that The fuel cell unit (1) comprises at least one encapsulation (68) for sealing and / or shielding the contact area (57) between the respective first and the respective second plain bearing component (51, 52) from the environment.

8. The fuel cell unit according to claim 7, It is characterized in that At least one space in the region of a respective one end (58, 59) of the contact region (57) between the respective first and the respective second plain bearing component (51, 52) is filled by means of a respective one encapsulation (68).

9. The fuel cell unit according to claim 7 or 8, It is characterized in that A respective sliding bearing (50) has two ends (58, 59) at the contact area (57) between the first sliding bearing component (51) and the second sliding bearing component (52), and both ends are sealed and / or shielded by means of a respective encapsulation (57).

10. The fuel cell unit according to any one or more of claims 7 to 9, It is characterized in that The encapsulation (68) is located on the first and second sliding bearing parts (51, 52) of a respective sliding bearing (50), in particular in the region of the ends (58, 59) of the contact region (57) between the first and second sliding bearing parts (51, 52).

11. A fuel cell unit according to any one or more of claims 7 to 10, It is characterized in that The geometry of a respective one of the contact regions (57) sealed by the encapsulation (68) corresponds substantially to the geometry of the encapsulation (68).

12. A fuel cell unit according to any one or more of claims 7 to 11, It is characterized in that The contact region (57) and the encapsulation (68) are designed to be annular and / or circular in cross section.

13. The fuel cell unit according to any one of claims 7 to 12, It is characterized in that The encapsulation (68) placed on a respective one end (58, 59) of the contact region (57) projects beyond the contact region (57) in a radial direction (72), in particular in both radial directions (72).

14. The fuel cell unit according to any one of claims 7 to 13, It is characterized in that The at least one encapsulation (68) is made of elastic plastic, preferably neoprene or rubber.

15. A fuel cell system (2) for converting chemical energy into electrical energy, comprising: - at least one fuel cell unit (1), - at least one oxidant supply system (26) for an oxidant; - at least one fuel supply system (29), - at least one cooling system; It is characterized in that The fuel cell unit (1) is designed according to one or more of the preceding claims.

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